Customized version of https://www.thingiverse.com/thing:3007147

Created with Customizer! https://www.thingiverse.com/apps/customizer/run?thing_id=3007147

Using the following options:

extrusion_width = 20
side_length = 30
side_thickness = 4
top_screw_count = 1
bottom_screw_count = 2
screw_hole_size = 5
screw_head_size = 10
recessed_screw_depth = 1
top_screw_elongation = 0
bottom_screw_elongation = 0
extrusion_insert_width = 0
extrusion_base = 20
wall_count = 2
max_wall_thickness = 0
cutout_size = 0
cutout_side_thickness = 3
extrusion_insert_count = 2
specific_bottom_nut_space = 0
bracket_angle = 90